Overview

Blood tests are very
common. When you have routine checkups, your doctor often orders blood
tests to see how your body is working. Many blood tests don’t require
any special preparations. For some, you may need to fast (not eat any
food) for 8 to 12 hours before the test. Your doctor will let you know
whether this is necessary.

During a blood test,
a small amount of blood is taken from your body. It’s usually drawn
from a vein in your arm using a thin needle. A finger prick also may
be used. The procedure is usually quick and easy, although it may cause
some short-term discomfort. Most people don’t have serious reactions
to having blood drawn.

Lab workers draw the
blood and analyze it. They use either whole blood to count blood cells,
or they separate the blood cells from the fluid that contains them.
This fluid is called plasma or serum. The fluid is used to measure different
substances in the blood. The results can help detect health problems
in early stages, when treatments or lifestyle changes may work best.

However, blood tests
alone can’t be used to diagnose or treat many diseases or medical
problems. Your doctor may consider other factors, such as your signs
and symptoms, your medical history, and results from other tests and
procedures, to confirm a diagnosis. Blood tests have few risks. Most
complications are minor and go away shortly after the tests are done.

Key Points

Blood tests
help doctors check for certain diseases and conditions. They also help
check the function of your organs and show how well treatments are working.

Blood tests
are very common. When you have routine checkups, your doctor often orders
blood tests to see how your body is working.

Some of
the most common types of blood tests that doctors order are full blood
count (FBC), blood chemistry tests, blood enzyme tests, and blood tests
to assess heart disease risk.

Many blood
tests don't require any special preparation and take only a few minutes.
Other blood tests require fasting (not eating any food) anywhere from
8to 12 hours before the test.

During a
blood test, blood usually is drawn from a vein in your arm or other
part of your body using a thin needle. It also can be drawn using a
finger prick. Drawing blood usually takes less than 3 minutes.

Once the
needle is withdrawn, you'll be asked to apply gentle pressure with a
piece of gauze or bandage to the place where the needle went in. This
helps stop bleeding. After a minute or two, you can remove the pressure.

The main
risks with blood tests are discomfort or bruising at the site where
the needle goes in. These complications usually are minor and go away
shortly after the tests are done.

Your doctor
should get the results of your blood test(s) and discuss them with you.
Blood tests show whether the levels of different substances in your
blood fall within a normal range. Your doctor should discuss any unusual
or abnormal results with you.